With the rapid development of data communication and wireless communication technology and the appearance of a large number of mobile terminals, more and more users wish to access the Internet efficiently and flexibly without being limited by time and space. The Internet is not only supposed to provide existing data services, multimedia audio and video services, but also realize function of a mobile Internet and provide a wireless Internet access service for a mobile terminal.
As the mobile terminal needs to roam between wireless access networks or fixed networks having structures different from the wireless access networks, seamless handover between the networks becomes a necessary requirement. Media independent handover (MIH) service is an Internet protocol (IP) handover service adapted to facilitate and optimize on heterogeneous networks. The mobile terminal may only detect surrounding network state information thereof, and global information of the whole network including a neighboring cell list and the like will be revealed by a network node. Thus, to realize handover of the mobile terminal between different networks, cooperation between the mobile terminal and the network node is required. The idea of the MIH is introducing one new protocol layer, namely, an MIH layer, which is located between a data link layer and a network layer. The MIH layer provides a service support for protocols of the network layer and upper layers thereof. At the same time, the MIH layer needs to use service supports provided by protocols of the data link layer and lower layers thereof. The MIH layer may provide three types of services, namely, event services (ES), command services (CS), and information services (IS). The MIH ES provides real time transmission services for events at lower layers of the link layer or events at a remote link. The MIH CS provides command transmission services to change bottom layer link state or a connecting point. The MIH IS provides information transmission services for network topology and location related information. Messages defined based on the three services are an MIH ES message, an MIH CS message, and an MIH IS message, respectively.
The MIH message is transmitted between an MIH client and an MIH server, so as to help achieve the seamless handover for the mobile terminal. Generally speaking, the mobile terminal including an MIH service entity is the MIH client, and the network node including the MIH service entity may serve as the MIH client and the MIH server at the same time. In a practical network deployment, the MIH service entity may exist separately, or may also coexist with other functional entities in a certain physical entity.
In the conventional art, a user-datagram protocol (UDP) and the IP are utilized for the transmission of MIH messages. FIG. 1 is a schematic view of a system for transmitting MIH messages in the conventional art. Referring to FIG. 1, the system includes an MIH client 110 and an MIH server 120. The MIH client 110 and the MIH server 120 each include an MIH service entity, a UDP transmission entity, an IP transmission entity, and an MIH timer.
A specific transmission process includes the following steps. An MIH message is generated by an MIH service entity 111 of the MIH client 110. The MIH message is sent to a UDP transmission entity 112. The UDP transmission entity 112 divides the received MIH message into a plurality of packets with the same length, encapsulates each of the packets into a UDP datagram, and sends the UDP datagrams corresponding to the packets to an IP transmission entity 113. The IP transmission entity 113 encapsulates each of the received UDP datagrams in an IP data packet, and sends out the IP data packets corresponding to the UDP datagrams. An IP transmission entity 123 of the MIH server 120 receives the IP data packets, removes an IP header of each of the IP data packets to obtain the UDP datagram, and sends the UDP datagrams corresponding to the IP data packets to a UDP transmission entity 122. The UDP transmission entity 122 removes a UDP header of each of the received UDP datagrams to obtain the packets of the MIH message, combines the packets into the MIH message, and sends the MIH message to an MIH service entity 121.
In addition, in order to ensure secure transmission, after the MIH service entity 111 of the MIH client 110 sends an MIH message, an MIH timer 114 is set for the message. After the MIH server 120 receives the MIH message, a response is made for the MIH message. The response message of the MTH message is returned to the MTH client 110, and when the response message is being returned, an MIH timer 124 also needs to be set.
When time of the MIH timer 114 of the MIH client 110 terminates, if the MIH service entity 111 of the MIH client 110 does not received the response message of the MIH server 120, the MIH message is retransmitted.
In the above-mentioned conventional solution, as the UDP is used as a bearer protocol for the MIH message, the flow control may not be realized by the UDP itself, so that the flow control function is not available for the transmission of the MIH message. In addition, in the method for transmitting the MIH message, a timer for a single MIH message is set, instead of setting a timer for a single packet of the MIH message, so that when a certain packet of the MIH message is lost, the whole MIH message has to be retransmitted, resulting in a low efficiency for the MIH message transmission.